Facial expression of children receiving immunizations: A principal components analysis of the child facial coding system

Objective: To identify the structure of facial reaction to procedural pain and to determine the subset of facial actions that best describe the response. Design: Observational. Setting: Five rural and five urban physicians' offices. Patients: One hundred twenty-three children aged 4 to 5 years undergoing routine diphtheria, pertussis, tetanus, and polio immunization. Outcome Measures: The Child Facial Coding System, comprising 13 discrete facial actions, was used to code each second of five 10-second phases from videotape: baseline, preneedle, needle, postneedle, and posthandling. Parents and a technician provided visual analog scale ratings of children's pain. Children provided a self-report using a Faces Pain Scale, and parents and nurses rated the children's pain and anxiety using visual analog scales. Results: A "pain face" similar to that reported in adults emerged with the onset of pain. Principal component analyses revealed the frequency and intensity of facial action during the needle phase could be represented by components reflecting pain sensation, a "brave face," and the children's expectations for pain. Children's Faces Pain Scale and adult visual analog scale ratings were best predicted by components reflecting pain sensation and expectations of high pain. Conclusions: These results provide a preliminary indication that the Child Facial Coding System can be reduced to components that reflect several aspects of children's acute pain experience and predict self-reports and observer reports of children's pain.